Gear pump having eccentrically arranged internal and external gears



Oct. 27, 1970 v c c, ALBRECHT ETAL 3,536,426

GEAR PUMP HAVING ECCENTRICALLY ARRANGED INTERNAL AND EXTERNAL .GEARS Filed April 5, 1968 2 Sheets-Sheet 1 I i I 1 v I A IN YEN TOR s CL/fi-ORD C. ALBRECHT L ESTER LE5 SMAL L 3,536,426 RICALLY ARRANGED RNAL GEARS Oct. 27, 1970 c. c. ALBRECHT I'A GEAR PUMP HAVING C INTERNAL A E r z Shqets-Sheefi 2 Filed April :5, 1968 INVENTOIRS CL/f'fORD CALBREcHr LESTER LEE SMALL 5v (1. 1:0 kw

United States Patent 3,536,426 GEAR PUMP HAVING ECCENTRICALLY ARRANGED INTERNAL AND EXTERNAL GEARS Cliiford C. Albrecht, Leicester, and Lester Lee Small, Spencer, Mass., assignors to Novelty Tool Co., Inc., Spencer, Mass., a corporation of Massachusetts Filed Apr. 3, 1968, Ser. No. 724,315 Int. Cl. F04c 1/06, 1/08 US. Cl. 418--166 4 Claims ABSTRACT OF THE DISCLOSURE A gear pump comprising an outer annular gear slidably meshing with an inner eccentrically mounted pinion gear having a lesser number of teeth. One of the gears is positively driven and the gears are so arranged as to cause the spaces between. the gear teeth to vary progressively in volume. Diametrically opposed fluid entrance and exit passages communicate with opposite sides of the gear teeth spaces so that for a given rotative speed an increase fluid flow is provided. The gears and associated parts may be oriented for either left-hand or a right-hand drive without aflecting the direction of fluid flow. To this end, the gear parts are reversely assembled in a cylindrical chamber with the driving shaft projecting at either end.

This invention relates to gear pumps for fluids and more particularly to that type which has an annular internal gear slidably meshing with an eccentrically mounted external gear of a lesser number of teeth, one of which gears is positively driven.

In pumps of this class, fluid is drawn from an inlet into gradually expanding spaces between the teeth and is forced into an outlet by the tooth spaces being progressively decreased in volume. The quantity of fluid thus transported depends, among other things, on the speed of rotation of the gears, the maximum volume of the gear spaces and the capacity of the inlet and outlet passages to fill and empty those spaces in the brief interval of time permitted. If these conditions were not right, there would be a tendency toward forming a partial vacuum at the entrance side and thus restricting the quantity oi fluid drawn in and delivered.

The primary object of this invention is to overcome that problem and to increase the fluid delivery capacity of a pump of a given gear diameter.

It is often desirable to drive such a pump from a motor located on either the leftor the right-hand side, and a further object is to provide a pump construction which can be reversed end for end to locate the driving axle on either side without interfering materially with the inlet and outlet connections and the pump operation, and which may be driven in either direction of rotation while maintaining the same direction of fluid flow.

Other objects will be readily apparent in the following disclosure.

Referring to the drawings illustrating one embodiment of the invention:

FIG. 1 is a sectional view of a pump which is driven by a motor connection on the left-hand end of the driving spindle;

FIG. 2 is a similar sectional view in which the pump parts are reversed to locate the driving spindle at the right;

FIG. 3 is a fragmentary sectional view on the line 3-3 of FIG. 1;

FIG. 4 is a view similar to FIG. 3 with the gears advanced to indicate the fluid flow;

ice

FIG. 5 is a fragmentary view on the line 55 of FIG. 1; and

FIG. 6 is a similar section on the line 66 of FIG. 1.

A gear pump of this general type comprises an annular gear 10 having inwardly projecting teeth 11 slidably meshing with the external teeth 12 of an inner gear or pinion 13 which is eccentrically mounted on a pin 14 relative to the axis of the outer gear. One of these gears, and preferably the outer annular gear 10 is positively driven, such as by means of a driving plate 15 connected to and driven by a spindle 16 which has an outer end 17 suitably shaped for connection with a motor, such as an electric motor of suitable characteristics. The fluid to be transported, which may be either a gas or a liquid, is introduced through an arcuate port 20 having suitable connections thereto and it is delivered through a similar outlet port 21. The eccentricity of the inner gear 13 and the shapes of the parts are such that as the outer gear 10 is positively rotated, the externally projecting teeth 12 of the inner pinion 13 progressively fill the spaces between the teeth 11 and then slidably recede to provide increasingly larger spaces within which fluid may be drawn. Similarly, as the gears rotate, those spaces are progressively de creased in volume for discharging the fluid therein. The inlet port 20 connects laterally with the spaces between the teeth, and they receive fluid from a suitable passage 24 in the lower half of the device. Similarly, the outlet arcuate passage 21 at the upper half of the casing connects laterally with the gear teeth spaces as they are progressively presented and discharges through an outlet 25.

Insofar as has been described, it will be appreciated that a pump, drawn to scale in FIG. 1, and which may have its outer gear rotated at usual speeds of 1750 or 3300 rpm. will necessarily have the gear thickness or axial dimension so limited that the gear teeth spaces can be filled with fluid in the small time permitted. Otherwise, a partial vacuum formed in the tooth spaces will tend to vaporize a liquid entering the pump. In accordance with this invention, access to that gear tooth space is provided at both sides of the gear, so that for a given size of inlet fluid passage the gear may be made wider, thus increasing the tooth space by that same degree, or the gears may be rotated more rapidly, with an increased delivery. To this end the inlet passage 24 is divided into suitably arranged channels in the casing, so that the fluid may enter the available gear tooth space laterally or from the passages 20 at both axially opposite sides, thus making it possible to increase the width axially of the gears or to drive them faster and so increase the pump capacity.

In further explanation of the structure, the gear pump may comprise a casing wall 30 having an outwardly projecting casting portion 31 provided with a central cylindrical cavity 32 within which the pump parts are removably located. An outer closure plate 33 at the right (FIG. 1) is suitably connected to the pump casing, as by tap screws 34, to seal that outer end. The axle pin 16 is mounted in a cylindrical plug 35 suitably located in the cylindrical opening 32 at the left. The driver axle 16 has an end lug 36 fitted into a slot 37 (FIG. 5) in the driver plate 15 so I that latter is positively rotated by the shaft 16. That plate 15 is connected, as by pins 38, with the outer gear 10, so that the latter is positively driven within the inner cylindrical surface 32 of the casting.

At the right-hand side of FIG. 1 is a cylindrical reversing block 40 rotatable within the cylindrical surface 32. That block 40 carries the pin 14 which is eccentrically located relative to the axis a of the driving spindle 16. The inner four tooth gear 13 is rotatably mounted on that pin 14. The eccentricity of the axis b of the pin relative to the axis a (FIGS. 3 and 4) is such that when one tooth C (FIG. 3) of the inner gear 13 fits into the space between two gear teeth of the outer five tooth internal gear 10, a diametriially opposite tooth E is slidably riding over a tooth on the outer gear 10.

The inlet and exit passages 20 and 21 are arcuate in shape and each subtends an angle of about 90 degrees as shown in FIG. 6. The passage 20 at the bottom and the one 21 at the top of the casing are so arranged that the gear spaces on opposite sides of the inner gear 13 successively connect with the inlets and outlets. The eccentricity of the pivot pin 14 forces the inner gear to enlarge the space F (FIG. 3) for the incoming fluid and decrease the space G for the outgoing fluid as the gears rotate in the direction of the arrow. It will be observed that the fluid has free access to the gear tooth spaces at the right hand side of the gear in FIG. 1 as indicated in FIG. 6. The driver plate 15 (FIG. is provided With arcuate slots 45 through which the fluid may pass to and from the passages 20 and 21.

The device is made reversible in rotative directions without affecting the direction of fluid flow. To that end, the block 40 which carries the eccentric pin 14 (FIG. 1) is provided with an external slot 48 extending peripherally through about 180 degrees. A pin or lug 49 fixed in the end plate 33 rides in the slot 48, and the parts are of such dimensions as to permit that block to rotate through about 180 degrees. This serves to move the center b (FIG. 3) of the pin 14 to the position c shown in FIG. 6, it being noted that the center in each location is about 45 from a vertical center line AA passing through the center a of the outer gear. A fluid passage 50 (FIG. 1) connects the outlet port passage 21 with the space between the block 40 and the plate 33 and thus transmits fluid pressure to the rear of the block, so that the latter is held in frictional contact with the outer driven gear 10. Thus, if the direction of rotation of the outer gear is reversed, the block 40 is rotated to change the location of the axis of the pivot pin 14- to a new location 0 shown in FIG. 6. A wavy washer 52 in the space between the block and the cover 33 aids in holding the block 40 toward the left and in contact with the driven gear during the operation.

It will now be appreciated that because of the symmetrical arrangement of the inlet and outlet ports and the fact that the various parts have outer cylindrical surfaces fitting within the cylindrical cavity 32, the construction of FIG. 1 may be reversed within the cavity 32 of the casing to provide the arrangement of FIG. 2 which 10- cates the driving shaft 16 at the right. This requires an end plate 55 bolted and sealed in place in the recess 56 (FIG. 1) of the casing 30. This plate carries the pin 57 corresponding with the pin 49 of FIG. 1, Which rides in the groove 48 of the reversing block 40 and thus controls the end angular position of the block 40 and the location of the eccentric pin 14 when the direction of gear rotation is reversed. The driving pin 16 in this rearranged construction projects outwardly through a central hole in an end plate 58. A ring shaped mechanical seal 59 prevents leakage around the shaft, and a coil spring 60 holds the block 62 in place relative to the pumping gears. That block 62 is constructed like the block 35 to provide the fluid passages and 21. The passage 50 provides outlet fluid pressure to hold the block against the driven gear 10 and thus position the axis of the pivot pin 14 at the point 0 shown in FIG. 6.

The operation of this type of gear pump follows the prior art in its general principles. As shown in FIG. 3, the inner gear 13 has each of its four teeth shaped to fit between any two of the outer gear teeth. That is, the gear tooth C in FIG. 3 seals off the space between the adjacent outer teeth. The spaces F around the tooth D communicate with the inlet 20, and the spaces G above the tooth E communicate with the outlet 21. Hence, as the gears rotate clockwise to the position of FIG. 4, another tooth B now meshes fully with the outer gear tooth space, again forming a barrier separating the inlet and outlet passages, so that fluid is continually entering the spaces F and is leaving from the spaces G. Hence, rotation of the gears in the direction of the arrow serves to force fluid from the multiple inlets to the outlets.

If the pump is to be driven from the right-hand side, as shown in FIG. 2, the outer gear 10' and its drive plate 15 as well as the bearing blocks are reversed in position, so that the driving spindle 16 projects at the right. That is permitted by the fact that the surface 32 of the casing is cylindrical and the parts are fitted accordingly. In either position of the block 40, fluid pressure is transmitted through the passage 50 to hold the block in its reversed position because of its friction against the driving gear.

It will now be apparently in view of the above disclosure that various modifications may be made in the structure within the scope of this invention.

We claim:

1. A rotary gear pump comprising a gear casing, an annular gear having inwardly projecting teeth rotatably mounted in said casing, an inner gear having one less tooth meshing with the annular gear teeth, a pivot for the inner gear within the casing mounted eccentrically of the axis of the outer gear, the eccentricity of the pivot and the shapes of the teeth causing the spaces between the revolving gear teeth to increase and decrease progressive ly, means including a driving shaft and plate for positively rotating one of the gears and thereby driving the other, said casing having diametrically opposed inlet and outlet passages which are radially opposite said gears and passages leading therefrom to axially opposite sides of the gears and communicating with the spaces between the gear teeth, so that fluid enters and discharges from said spaces substantially equally from both sides as the gears are revolved, said driving plate being in a plane normal to said pivot.

2. A rotary gear pump comprising a casing having outer faces and an opening therethrough providing an internal bearing surface extending between said faces and inlet and outlet passages on diametrically opposite sides of the axes of said surface, an annular gear having internal teeth and an external cylindrical surface rotatably mounted on said bearing surface and insertable therein from either side of the casing, an inner gear having external teeth one less in number than said internal teeth and arranged for meshing therewith, an axle removably mountable in said opening for selectively projecting from the opening at either side of the gears which is connected to drive one of said gears and a pivot for said inner gear which is mounted with its axis eccentric to the axis of the annular gear, said eccentricity and the gear teeth spaces being such that the gear teeth progressively mesh and pump fluid from said inlet to the outlet passage when the gears are rotated.

3. A rotary gear pump comprising a casing having an opening therethrough providing an internal cylindrical bearing surface and inlet and outlet fluid passages on the opposite sides of the axis of said surface, an annular gear having internal teeth and an external cylindrical surface rotatably mounted on said bearing surface, an inner gear having external teeth one less in number than said internal teeth and arranged for meshing therewith, a reversing block having an external cylindrical surface rotatable through a limited angle on said internal surface which is removably insertable in said opening on either side of the gears, an arbor carrying said external gear which is mounted on said block eccentrically relative to said internal gear, an axle plug within said bearing surface, and an axle rotatably carried by said plug which selectively projects from the opening at the opposite side of the casing from said block which is connected to drive one of said gears, said eccentricity and the gear teeth spaces being such that the gear teeth progressively mesh and pump a fluid from said inlet to the outlet passage when the gears are rotated and whereby the fluid flow will be in the same direction irrespective of the direction of rotation of the gears.

4. A rotary gear pump comprising a gear casing having an opening therethrough providing an internal cylindrical surface, an annular gear having an outer cylindrical surface mounted to rotate within said internal cylindrical surface and having inwardly projecting teeth, an inner gear mounted Within and meshing with said teeth, an axle mounted within said opening which selectively projects from either end thereof, means for connecting the axle in the selected position to one of the gears for rotating the same, a reversing block mounted for a limited rotary movement through 180 degrees, and a pivot on said block which holds the inner gear eccentric relative to the internal gear in a position dependent on the position of the reversing block whereby the fluid flow is unidirectional for either rotative direction of the axle, said casing having external inlet and outlet fluid passages and internal passages leading from said fluid passages to axially opposite sides of the gears and communicating with spaces between the gear teeth, so that fluid enters and discharges from said spaces substantially equally from both sides as the gears are revolved.

References Cited UNITED STATES PATENTS 1,768,818 7/1930 Bock. 2,433,360 12/1947 Haight. 2,778,316 1/1957 Haightetal. 3,303,783 2/1967 Neubauer. 3,303,784 2/1967 Neubauer. 2,180,218 11/1939 Wissman 192 18.1 2,506,842 5/1950 Rockwell 192 17.1 2,880,834 4/1959 Gerst. 15 3,129,960 4/1964 Schrodt 285-14X HENRY F. RADUAZO, Primary Examiner 

